I'm trying to teach myself calculus and have come across this problem.
I have a function of x
f(x) = x^3 + 5x^2 - 8x - 12
so I set this to zero by
f'(x) = 3x^2 + 10x - 8 = 0
then the book I'm using says that I can find the local values of x for min and max and these should be x1 = 0.667 and x2 = -4.000 but it doesn't say how these figures are reached.
Could someone guide me in the right direction please.
Thanks in advance
The "x" solutions are simple to see if you can write your sum of 3 terms as a product by factoring to
We take the factors of -8 that sum to 10 when multiplying out the brackets.
This is (3)4+1(-2) and so
then those factors are giving you the 2 solutions
Thanks for the quick reply, it has been a great help. However the answers in the book are 0.667 and -4.000 but I end up with -1.33 and -2.
I'm either losing the plot entirely or having finger trouble, could someone possible check my maths please.